The invention relates to a foamable composition comprising at least two parts. More specifically, the first part comprises at least one polyol, at least one thixotropic gelling agent, and at least one blowing agent wherein the first part comprises an effective amount of hydrophobic ingredients and a second part comprising at least one isocyanate. A foam mass can be prepared by a method of combining the polyol component with the isocyanate component substantially free of urethane prepolymer and applying the mixture to a void or substrate. The invention also relates to methods of using the foamable composition in the repair of surface defects or for the reinforcement of structural members such as spike holes left after spike removal from railroad ties during road bed maintenance or repair. The invention further relates to a method of foaming the composition in the presence of water.
Materials used to repair defects in structural members should have certain characteristics. The material should be easily applied and should form high strength bonds to structural members made of varying materials. Particularly for outdoor repairs, the repair materials should be usable in many environments including environments having extremes of heat and cold and having the presence of substantial quantities of environmental water.
One particularly important end use for such repair compositions is in the recycle or reuse of railroad ties. Typically in the maintenance of the railroad right of way, the rails along with the tie plates and spikes, are removed from railroad ties which remain in the roadbed. If a new rail is to be spiked to the old tie, it is critical that the railroad tie spike holes be repaired prior to laying the new rail. The presence of spike holes in an old tie can cause problems since if a spike is driven into a portion of the tie near an old spike hole, the driving force of the spike can displace the spike from its intended location into an old hole, displacing the rail, tie plate and spike. In the instance that the spike is driven into an incorrect location substantial economic loss can result in repairing the misaligned rail. If a misaligned rail is not repaired, the defect can cause derailment or other problems. Further, the spike holes can be the source of structural weakness in the tie, allowing water to enter the core of the tie accelerating the degradation.
Mechanical spike hole repair means have been suggested in the art. For example, Moses, U.S. Pat. No. 3,191,864, issued Jun. 29, 1965 teaches a mechanical spike hole insert used by first boring out an old spike hole, installing an insert and driving a new spike into the insert. Newman U.S. Pat. No. 3,716,608, issued Feb. 13, 1973 teaches metallic inserts that can be placed in bored out spike holes with a filling of a synthetic resin into which the spikes can be driven. In another area of repair, Tessenski, U.S. Pat. Nos. 4,070,201 and 4,152,185, issued Jan. 24, 1978 and May 1, 1979 respectively, teach a railroad tie spike hole plugging material and method using a substantial uniform mixture of a granular abrasive material and a granular plastic material which is poured into the hole left after spike removal. The driving force of a spike into the abrasive material generates heat which plasticizes the material resulting in a firm bond of the spike to the material. Mechanical and resin-based hole filling methods tend to be time consuming, expensive and adapted to manual, not automatic application or installation.
Rhodes et al., U.S. Pat. No. 4,295,259, issued Oct. 20, 1981, teaches a method of reusing wooden railroad ties in which the old spike holes are filled with a high-density rigid polyurethane foam injected into the holes. At col. 4, lines 14-20, this reference states that xe2x80x9cManufacturers of polyurethane chemicals caution that both components not be allowed to drop below 55xc2x0 F. (13xc2x0 C.) at any time, including shipping and storage. Temperatures below 55xc2x0 F. (13xc2x0 C.) apparently have a deleterious effect on the properties of the final product. Temperature control during operation is used to regulate viscosity.xe2x80x9d
Other polyurethane foam compositions have been suggested for other uses. For example, Maruyama et al., U.S. Pat. No. 4,264,743, issued Apr. 29, 1981, teaches a polyurethane foam sealing material prepared from a polyisocyanate and a polyol component, a major portion of said polyol component consisting of polyol derived from a dimer acid or castor oil, or a mixture thereof in the presence of a blowing agent, a foam stabilizer, a catalyst, and optionally, a lipophilic filler. As the catalyst, tertiary amines and organotin compounds are preferably used. The sealing materials are suitable for use in fender, ventilator, air conditioning joints and other parts in automobiles, as well as in ships, refrigerators and other assembly products.
Barker et al., U.S. Pat. No. 5,124,367, issued Jun. 23, 1992 teaches a fire retardant composition comprising a dispersion of solid fire retardant additive in a liquid isocyanate-reactive compound having a functionality of from 2 to 8 and an average equivalent weight of from about 31 to about 5000 and, as an anti-settling agent, an effective amount of a fatty acid ester and/or amide such as castor oil. The anti-settling agent is disclosed in an amount of 0.05 to 5%. The composition is useful in the manufacture of fire resistant flexible and rigid foams.
Grimm et al., U.S. Pat. No. 5,470,515, issued Nov. 28, 1995, teaches insulating pipes by application of at least one insulating layer and at least one outer surface layer by rotational molding. A rigid polyurethane foam is used as the insulating layer while a solid polyurethane is used as the surface layer. The rigid polyurethane foam is obtained by the reaction of a) an aromatic isocyanate with b) a polyol component bearing on average at least 3 isocyanate-reactive hydrogen atoms containing: 1. a polyether containing at least two hydroxyl groups and having a molecular weight of 300 to 700, 2. an aliphatic, cycloaliphatic or aromatic polyamine having a molecular weight of 32 to 1,000 as a crosslinking agent and a blowing agent, and optional ingredients. The solid polyurethane is obtained by the reaction of a) an NCO-terminated prepolymer having an NCO content of 5 to 20% obtained by the reaction of 1) 4,4xe2x80x2-diphenyl methane diisocyanate, optionally admixed with 2,4xe2x80x2 and 2,2xe2x80x2-isomers and 0 to 30% by weight components of high functionality with; 2) polyethers containing 2 to 4 OH groups having a molecular weight of 1,000 to 6,000 to which up to 30% by weight of a hydrophobicizing agent, preferably castor oil, has optionally been added with b) a polyol component containing 1) a polyether containing 2 to 4 isocyanate-reactive hydrogen atoms and having a molecular weight of 1,000 to 6,000; 2) 5 to 35% by weight of an aromatic diamine having a molecular weight of 122 to 400; 3) 0 to 5% by weight of an aliphatic or cycloaliphatic diamine having a molecular weight of 60 to 4000; 4) 0 to 30% of a hydrophobicizing agent and 5) optionally auxiliaries and additives.
Doyle et al., U.S. Pat. No. 4,248,811, issued Feb. 3, 1981, teaches equipment and formulations for the filling of ordinary pneumatic tires with a polyurethane foam. Exemplified is a composition wherein component A contains 4,4xe2x80x2-diphenylmethane diisocyanate (MDI) 5 equivalents 665 lbs. and hydroxy-terminated polybutadiene 1 equivalent 1250 lbs. and component B contains hydroxy-terminated polybutadiene 1.1 equivalents 1375 lbs., castor oil 1 equivalent 340 lbs, 1,4-butanediol 1 equivalents 80.1 lbs, silicone surfactant 35 lbs, tertiary amine catalyst 4.5 lbs., lead octoate catalyst 4.5 lbs, and tall oil fatty acid 30.0 lbs. The castor oil is added to compatibilize the polybutadiene.
The use of polyurethane foam in filling spike holes in used railroad ties can present significant problems. The polyurethane foam compositions do not appear to adhere to a spike hole with sufficient adhesion to prevent the accidental removal of the foam repair mass during the repair and subsequent mechanical rail installation. Further, the urethane foams of the prior art tended to foam uncontrollably in the presence of substantial environment moisture. Since moisture tends to accelerate the foaming properties of the urethane composition, the presence of water can cause too rapid of cell expansion resulting in a foam mass of low strength and low density which can result in the formation of an incomplete or unreliable repair of structural members.
Morin, U.S. Pat. No. 4,661,532, issued Apr. 18, 1987, teaches coal tar containing foaming urethane compositions and a method of repairing defects in structural components. A two package hydrophobic urethane foaming composition is disclosed in which the first package comprises a polyol made hydrophobic by the presence of an effective amount of a coal tar or coal tar pitch composition. Although the use of coal tar significantly improved the problems associated with adhesion and uncontrolled foaming of the polyurethane composition in the presence of substantial moisture, this approach has had limited commercial success due to worker safety hazards since coal tar has been identified as a carcinogen. Hence, products were developed in which the coal tar was replaced with a mixture of hydrophobic polyols comprising about 20 wt-% castor oil present in the polyol component. The viscosity of each part of such products is about 2,000 cPs at 77xc2x0 F. (25xc2x0 C.), but increases to about 50,000 cPs at 50xc2x0 F. (10xc2x0 C.), and in the excess of 100,000 cPs at 40xc2x0 F. (4xc2x0 C.). Hence, the coal tar containing compositions as well as the non-carcinogenic modifications were found to be difficult to apply by conventional application equipment without the addition of heat. The recommended application temperature for such products ranged from about 130xc2x0 F. (54xc2x0 C.) to about 140xc2x0 F. (60xc2x0 C.). As railroad repair becomes a year-round task, rather than seasonal during warmer months of the year, the difficulty in application became quite problematic.
Accordingly, a substantial need exists in the art for foamable compositions employing non-carcinogenic ingredients that can be used to repair surface defects on structural components such as railroad ties to provide a repair mass having strong adhesion to the substrate structural member, which can be used in the presence of substantial quantities of environmental water and can be used in automatic application equipment in all temperatures.
The invention features a foamable composition that can be foamed in the presence of high concentrations of water. The foamable composition builds viscosity and forms a thixotropic gel sufficiently fast enough that it can be foamed in the presence of environmental water, or even underwater, while still maintaining excellent foam quality such as consistent foam structure, high strength and high foam density. The foamable composition exhibits excellent adhesion to a variety of substrates including plastic, metal and wood, even when such substrates are wet or under water.
In one aspect, the present invention is a foamable composition having at least two parts comprising:
a) a part A comprising at least one polyol, at least one gelling agent, and at least one blowing agent; wherein the part A comprises an effective amount of hydrophobic ingredients; and
b) a part B comprising at least one isocyanate.
Preferably, the polyol is castor oil and the gelling agent is a polyamine. Further, the polyurethane composition preferably further comprises at least one plasticizer in part A and/or part B to reduce the viscosity as well as certain catalysts to attain the proper reaction rates after mixing and application. Advantageously, each part exhibits a low viscosity over a wide temperature range, having a Brookfield viscosity of less than about 10,000 cPs at temperature ranging from about 20xc2x0 F. (xe2x88x927xc2x0 C.) to 40xc2x0 F. (4xc2x0 C.).
In another aspect, the invention further relates to a foam mass prepared by a method of:
a) forming a mixture comprising a polyol component comprising at least one polyol, at least one gelling agent, and at least one blowing agent and an isocyanate component substantially free of prepolymer;
b) applying the mixture to a void or substrate.
In this embodiment, the isocyanate component is preferably substantially free of isocyanate reactants to avoid the formation of a prepolymer which tends to substantially increase the viscosity of the isocyanate component.
In a preferred embodiment the present invention further relates to a foamable composition comprising:
a) a part A comprising an amount of 30 wt % or greater of at least one hydrophobic polyol, at least one gelling agent, and at least one blowing agent; and
b) a part B comprising at least one isocyanate.
Another aspect of the present invention is to provide a polyurethane foam composition that is substantially unaffected by variations in the concentration of blowing agent such as water. It is surmised that the hydrophobic agent and moisture form an equilibrium at the exterior surface of the foam limiting the further take-up of moisture.
In yet another aspect, the invention features a foamable composition comprising at least two parts:
a) a first part comprising at least one polyol; at least one thixotropic gelling agent; at least one blowing agent; at least one urethane reaction catalyst; and at least one isocyanurate reaction catalyst, and
b) a second part comprising at least one isocyanate.
The composition can be formulated such that the polyol, preferably, does not contain any ester linkage, such as the ester linkage in castor oil or its derivatives. The composition can also be formulated such that there is no hydrophobic ingredient included. Further, the composition can be formulated to exhibit, upon machine mixing the first part and the second part, instant thixotropic gelling so that it is controllably foamable in the presence of a large amount of environmental water, and even under water. The composition can also be formulated to exhibit, upon foaming under water, very high wet foam density that is substantially the same as dry foam density.
In yet another aspect, the invention relates to a method of repair or reinforcement of a structural member comprising the steps of:
a) providing a structural member having a void;
b) providing a foamable composition comprising a mixture of:
i) a first part comprising at least one polyol, at least one gelling agent, and at least one blowing agent; wherein the first part comprises an effective amount of hydrophobic ingredients and
ii) a second part comprising at least one isocyanate;
c) applying the mixture to the void.
The composition initially has a relatively low viscosity upon mixing. However, the applicant surmises that the thixotropic nature of the polyamine causes the composition to attain the proper consistency for good repair or reinforcement almost immediately upon application. Since the consistency of the foam relies on a chemical reaction, the thixotropic nature of the composition, rather than merely the initial viscosity of the blended parts, the composition may be easily applied at temperatures ranging from about xe2x88x9220xc2x0 F. (xe2x88x9229xc2x0 C.) to about 120xc2x0 F. (49xc2x0 C.).
In yet another aspect, the invention further relates to a method of foaming a polyurethane composition underwater comprising the steps of:
a) providing a substrate submerged in an aqueous environment;
b) providing a polyurethane composition in an applicator having an exit port, said composition comprising:
i) a first part comprising at least one polyol, at least one gelling agent, and at least one blowing agent; wherein the first part comprises an effective amount of hydrophobic ingredients, and
ii) a second part comprising at least one isocyanate;
c) blending the first and second part to form a mixture;
d) submerging the exit port in said aqueous environment;
e) applying the mixture to said substrate.